Chemistry Thermochemistry quiz

What is heat?

Energy transferred between two substances due to a temperature difference. Flows from higher to lower temperature. SI Unit: Joules (J).

What is specific heat?

• The energy required to raise the temperature of 1 g of a substance by 1°C. Specific Heat of Water: 4.18 J/g°C4.18J/g°C.

What are endothermic?

Endothermic: Uses heat(+ΔH)

exothermic reactions?

Releases heat (-ΔH)

What is entropy?

A measure of disorder in a system.

Factors affecting entropy:

• Temperature: Higher temp = more disorder.

• State of Matter: Gases > Liquids > Solids.

• Number of Molecules: More molecules = more entropy.

• Types of Molecules: More varied substances = more entropy.

What is Gibbs Free Energy?

The amount of energy available to do work

Gibbs Free Energy formula?

ΔG=ΔH−TΔS

Negative ΔH and Positive ΔS.

Always Spontaneous

Positive ΔH and Negative ΔS.

Never Spontaneous

Negative ΔH and Negative ΔS.

Low Temp Spontaneity

Positive ΔH and Positive ΔS.

High Temp Spontaneity

How to calculate enthalpy by heats of formation?

ΔH=ΣHf(Products)−ΣHf(Reactants).

How to calculate enthalpy by Bond Energies:

ΔH=(Bonds Broken)−(Bonds Formed).

How to calculate enthalpy by Hess’s law?

Combine enthalpy changes from multiple reactions.

What is activation energy?

Activation Energy (EA): The minimum energy required for a reaction to occur.